The present invention generally relates to semiconductor devices and more particularly to a substrate for carrying a semiconductor chip and a manufacturing method thereof. Further, the present invention is related to a semiconductor device that uses such a substrate.
With sharp increase of clock frequency in recent advanced semiconductor devices, supply of a stable electric power to semiconductor chip is becoming a paramount problem. In order to deal with this problem, there is a proposal to provide a capacitor on a substrate on which the semiconductor chip is mounted.
FIG. 9 shows a conventional semiconductor device 10.
Referring to FIG. 9, the semiconductor device 10 includes a substrate 11 mounted with a semiconductor chip 12, wherein the substrate 11 includes a substrate body 13 and a decoupling capacitor 14. The decoupling capacitor 14 is provided inside the substrate body 13. The decoupling capacitor 14 includes a dielectric film 16 formed on a silicon substrate 15, and a conductive film 17 is provided further on the dielectric film 16. Reference should be made to Japanese Laid-Open Patent Publication 2001-274034.
In such a semiconductor device 10, which uses a separate capacitor component for the decoupling capacitor 14 in the state that the capacitor 14 is embedded in the substrate body 13, it is difficult to reduce the distance between the decoupling capacitor 14 and the surface on which the semiconductor chip is mounted. In other words, the semiconductor device 10 has a drawback in that reduction of the inductance between the decoupling capacitor 14 and the semiconductor chip 12 mounted on the substrate 11 is difficult. Associated with this drawback, there arises a problem that supply of stabilized electric power, particularly the supply of stabilized voltage, to the semiconductor chip becomes difficult because of the existence of the inductance. This problem becomes particularly serious in recent high-speed semiconductor devices in which the semiconductor chip is driven at a very high clock speed.
In the foregoing prior art, it should be noted that a discrete capacitor component formed separately to the substrate 13 is used for the decoupling capacitor 14, while the decoupling capacitor 14 has to be provided in the form embedded inside the substrate body 13. Because of such a construction, the conventional semiconductor device 10 shown in FIG. 9 has suffered from the problem of complex manufacturing process and the associated problem of high manufacturing cost.
In addition, because the capacitor 14 is formed as a discrete component, a silicon substrate has to be used for the silicon film 15 for supporting the capacitor structure thereon. Associated with the use of such a silicon substrate, there arises a problem that a dicing process becomes necessary for separating the capacitor components 14 formed on a common silicon substrate, while such a dicing process also increases the cost of the substrate 11.
Further, associated with the use of silicon substrate for the silicon film 15, there arises a problem in the semiconductor device 10 in that the decoupling capacitor 14 cannot be formed as thin as desired, and because of this, the thickness of the substrate 11 has been increased. In order to avoid unwanted increase of thickness of the substrate 11, the substrate body 13 is formed with a depression 18 in the example of FIG. 9. However, formation of such a depression 18 makes the manufacturing process and structure of the substrate 10 very complex.